[Editing] Fix triple-click selection extending beyond table cell
boundaries

Triple-clicking text inside table cells was selecting content beyond
the cell boundaries, including unwanted table structure. This caused
copy/paste operations to include table markup instead of just the cell
content.

Added table cell boundary constraint in selection adjuster for
paragraph granularity selections, checking EnclosingTableCell() in
ComputeEndRespectingGranularityAlgorithm() and returning early when
selection end is within a table cell.

Bug: 40852213
Change-Id: I5a5dec4beb2ee3c9410b1a2d78e289e5c32e1471
Reviewed-on: https://chromium-review.googlesource.com/c/chromium/src/+/6904826
Reviewed-by: Utkarsh Pathak <utpathak@microsoft.com>
Reviewed-by: Kent Tamura <tkent@chromium.org>
Commit-Queue: Tanu Jain <tanujain@microsoft.com>
Cr-Commit-Position: refs/heads/main@{#1527948}